Hours before the Baltimore Ravens and the San Francisco 49ers faced off in Super Bowl XLVII Sunday night, two American superstar vocalists took the stage at Symphony Hall. It wasn’t a case of dueling divas, however: Soprano Renée Fleming and mezzo-soprano Susan Graham hugged a lot, and they complemented rather than competed with each other.

Both were in glorious voice; there wasn’t a single power outage. What’s more, as Graham remarked in a pointed reference to Beyoncé’s Inauguration performance before the fourth and final encore, “I guarantee you we have sung every note live.” In the end, this Celebrity Series event was a super show in which there were no losers.

It was even educational. It began with a bit from a taped interview with Mary Garden, an American soprano who enjoyed success in Belle Époque Paris, and almost the entire afternoon was devoted to French composers. In lieu of program notes, Fleming and Graham provided witty commentary. Graham said of Garden and Sanderson, “They were stunning dramatic divas, on stage and off.” Pause for a significant glance at Fleming. “Some things never change.”

The opening numbers were duets by Saint-Saëns and Fauré, the divas leaning into each other at the words “Aimons toujours,” from Saint-Saëns’s “Viens! Un flûte invisible,” then standing back to back, arms folded, as they prepared to pussyfoot their way through Fauré’s “Pavane.” Their voices blended so beautifully as to be indistinguishable. Graham is the more extroverted of the two onstage; Fleming doesn’t move about as much, but she’s as expressive in her own contained way. Before intermission, Metropolitan Opera assistant conductor Bradley Moore played Debussy’s “Clair de lune” in a performance that was short on moonlight; throughout the afternoon he was a sympathetic but slightly hard, literal piano accompanist. Fleming then sang two pieces by Debussy and sauntered, teasing, through Delibes’s bolero “Les filles de Cadix.”

After intermission, Graham came out in silver — both ladies had worn black in the first half of the program — and remarked, “Two divas, four dresses — you get what you pay for.” Her solo spot consisted of four songs by one of her favorite composers, Reynaldo Hahn; she was nightingale-melodious in “Le rossignol des lilas.” Then Fleming returned in tomato-red and they resumed their sister act — literally in the first encore, “Ah, guarda, sorella,” from Mozart’s “Cosí fan tutte.” For her solo encore, Graham accompanied herself ably at the piano in a rendition of “La vie en rose” that was no shrinking violet; Fleming riposted with a sly “Malheureux qui a une femme,” from the “Chants d’Auvergne.” They finished this vocal Super Bowl with another sibling duet, the tender “Evening Prayer” from Humperdinck’s “Hansel and Gretel.” Too bad the afternoon couldn’t have lasted as long as the football game did.

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